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Astron. Astrophys. 325, 542-550 (1997)

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2. Observations

The 1300 µm mapping was carried out at the IRAM 30 m telescope during two bolometer sessions in February 1993 and March/April 1995. In the first session we used the MPIfR 7-channel bolometer array. The atmospheric conditions were good to average with an optical depth between 0.15 and 0.26; the pointing was stable, giving an accuracy of about 3 [FORMULA], rms. The calibration was mainly done on Mars (3 maps) and Uranus (1 map). The overall system sensitivity was 50 mJy Hz [FORMULA]. Typical map sizes were 2 [FORMULA], by 2 [FORMULA], (in Az,El), some were larger with 3 [FORMULA], by 3 [FORMULA]. We used wobbler throws of 32 [FORMULA], or 44"; the beam size of a single channel was 11 [FORMULA], (HPBW). The mapping was carried out at a scanning speed of 4 [FORMULA] with a separation of 4 [FORMULA], between the scanning lines.

During the second session we had the opportunity to use the MPIfR 19-channel bolometer. The atmosperic conditions were similar, with [FORMULA] -values between 0.16 and 0.3. The pointing accuracy was about 3 [FORMULA], rms. Mars (2 maps) and Uranus (2 maps) served again as calibration standards. The sensitivity was slightly better than in the previous run, giving about 40 mJy Hz [FORMULA]. The map sizes were 3 [FORMULA], by 3 [FORMULA], the wobbler throw was set to 32 [FORMULA], and the beam size was again 11 [FORMULA], (HPBW). We worked at a scanning speed of 5 [FORMULA] and the scanning lines were separated by 4 [FORMULA]. We estimate our absolute photometric accuracy at 1300 µm to be of the order 20%.

The 350 to 2000 µm photometry for HH 114 MMS was performed at the James Clerk Maxwell Telescope 1 (JCMT) on Mauna Kea, Hawaii, from February 25 until March 1, 1994. The detector was the UKT14 receiver (Duncan et al. 1990). Observations were carried out with a constant aperture of about 18 [FORMULA]. The secondary mirror was chopped in azimuth at [FORMULA] Hz with a beam separation of 70 [FORMULA]. Calibration was performed by measuring Uranus (Orton et al. 1986, Griffin & Orton 1993), and the secondary calibrators NGC 2071IR and W3(OH)(Sandell 1994). We used a similar calibration method to that outlined by Stevens & Robson (1994). The 225 GHz opacity at zenith was [FORMULA] and remained stable throughout a single shift. We estimate our total absolute calibration uncertainty for the JCMT observations to be [FORMULA] 30%. Pointing and focus checks were performed typically once per hour.

The IRAS Point Source Catalog lists flux densities for HH 114 (IRAS 05155+0707) at all four wavebands. However, this source is not coincident with HH 114 MMS. Therefore we obtained the IRAS Calibrated Reconstructed Detector Data (CRDD) of the region, which consists of the time sequence data streams from each detector (for details of the IRAS focal plane detector arrangement see Fig. II.C.6 of Beichman et al. 1988), and made images from the individual IRAS detectors using the UK Starlink software package IRAS90 (e.g. Ward-Thompson et al. 1989; Ward-Thompson & Robson 1990). We failed to find a point source coincident with HH 114 MMS, but we performed photometry on these data using a 3 [FORMULA], aperture, and thereby estimated upper limits to the IRAS flux densities of HH 114 MMS.

We selected the strongest sources from Paper I and included HH 212 in the present investigation. Table 1 gives the positions and various 1300 µm flux densities of all sources as derived from Gaussian fits to the maps in Fig. 6. Table 2 contains the FIR and submm fluxes for HH 114 MMS. When comparing [FORMULA] (column 9) in Table 1 with the corresponding flux densities of Paper I, one finds on the average that the new values tend to be higher than the old ones. This is partly due to a combination of a better positional accuracy and a better background subtraction, both obtained by the mapping procedure. In addtion, some extended sources could not be measured properly by the earlier single beam ON-OFF measurements. While this increase in flux has no influence on the luminosity of the sources as quoted in Paper I, the dust mass has to be increased formally by about 50% for some of the sources. Taking into account, however, that the unknown dust properties in these dense environments introduce an error that might be a factor 5 to 10 above the standard values, we do not consider it necessary to recalculate the corresponding dust masses. The conclusion of Paper I, concerning the flat shape of the spectral energy distributions is even strengthened by the increase of the 1300 µm flux densities.


Table 1. 1300 µm mapping of HH energy sources


Table 2. FIR and submm photometry of HH 114 MMS.

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998